True of terms denoting the bottom object, usually meaning that a function is undefined on given arguments. There is exactly one object in the universe of discourse that is undefined, called BOTTOM. Functional terms that are undefined are equal to this special element.
- UNDEFINED is not in the KIF 3.0 spec, but is implicitly there.
(<=> (Undefined ?Value) (= ?Value Bottom))
(Inherited-Slot-Value@Frame-Ontology Undefined = Bottom)
(<=> (Defined ?X) (Not (Undefined ?X)))